Series 3 Transmission Trouble
 

Hoping someone can point me in the right direction with a problem with the transmission on my 1972 V12 auto. As far as I know the automatic gearbox is the original Borg Warner Model 12.
A month or so ago I was driving the car around the storage area where I keep the car. With no warning, I lost the drive, with a noise (didn't sound catastrophic, but it was there), and the engine revs increased significantly (not as far as redline).
Trying different selector positions, I found that reverse still worked fine. For another few feet, I still had some drive in position 2 on the selector, but then that stopped aswell.
I got the car back into the garage in reverse, with no further issues.
Since then, because I still had motion in reverse, I've been slowly adding transmission fluid to the 'box. So far I've added 2 pints (capacity is 16 pints).
When checking for any progress today, once the car was warmed up, I still have reverse but can only get a creep forward in drive. However, positions 1 & 2 on the selector both give me "normal" positive forward motion (position 2 had stopped originally!).
Reading through the fault diagnosis section of my repair manual, the only check that it suggests for no forward drive in D, other than those suggested for the other selector positions is to check the rear band adjustment. I can't find any detail about how to check this in the manual, so assume it's a transmission strip-down check.
Has anyone experienced anything like this, and, if so, how did you fix it?
Having got drive back in selector positions 1 & 2, I'm tempted to continue topping up the fluid, but I don't want to run the risk of over-filling the 'box, although it is vented through the dipstick/filler tube, so worst case I would only expect it to spit fluid back up through that.

I think 'check band adjustment' is an odd statement. IMO, you don't check the band adjustment. You just go ahead and adjust the band.

As far as I know it's a matter of loosening the lock nut, turning the adjuster down until it is snugly seated, then backing off the adjustment 1/2 turn. The tighten the lock nut. Cleaning the area first with aerosol brake wash or similar is a good idea.

I presume there's no conventional transmission dipstick in the engine bay to check the level? It's an older design where you have to pull back the carpet to remove an access panel....to access a shorty dipstick?


If the latter is true then that's really your best bet, although inconvenient

Cheers
DD

Thanks Doug.
I'll look into adjusting the band.
Regarding the dipstick, it's at the back of the engine bay, so easily accessible. my issue is whether I should be reading it hot or cold. With the engine cold, after putting in the two additional pints of fluid my level is just over max. However, a mechanic I was talking to about this suggested that I should be checking the level with the transmission warm - in this case, the level looks below min. There's a small leak from under the transmission, so I guess I could have lost 2 pints over the time I've had the car, although it's not pouring out - the majority of the ATF I've just put in is still in there. If the problem is fluid level, I'm surprised it stopped driving as quickly as it did. Having said that, the only thing I've changed so far is to add in fluid, and that has brought back the drive in selector positions 1 & 2, even though I still don't have D.
Anyway, I'll try the adjustment and see where we go from there. Thanks again.

Trans fluid level should be checked when hot. Not warm, not cold. Hot. With engine running, transmission in "P".

The level increases when hot.... by a couple pints or even more.


Cheers
DD

It took me a long time to finally get round to sorting out the transmission on my car. I had found a good mechanic, and decided to get him to do a lot of the work that I don't have the facilities to do, so for one of those jobs, I asked him to check out the transmission. Turns out that by taking the bottom cover off the transmission, it also gives access to the input and output shafts. My mechanic was able to determine that it was a one-way clutch (or Spragg bearing) that drives first gear that had failed, and was therefore not allowing any drive in first gear.
My mechanic was able to drop the gearbox out from under the car - fortunately without removing the engine (it was a tight squeeze to get it back in again, working against gravity, bu he and his team did it!) - and make the necessary repairs.
Even though we could see the one-way clutch on gearbox drawings, we weren't able to find a spec for it. Fortunately, my mechanic had an old transmission from an S3 E-type in his shop, so took the one-way clutch from that one and installed it in mine. I now have to take the old one and try to spec it for a replacement for his unit.
So the car is now running fine, and I'm looking forward to the snow we now have to leave, so I can properly enjoy the car on the road.

glad to hear you figured it out. Maybe we'll see you on the road in the spring - there's an early British car show in Ancaster April 22.

Canadian car (Toronto area), 1974 OTS, Borg Warner Model 12 transmission. I am having an issue with 2nd to 3rd shift, or rather no shift. Runs good, reverse normal, 1st to 2nd normal. Just cannot get it into 3rd, including trying to upshift manually to D. I have read through the various threads and first assessment is to look at linkages and vacuum modulator/vacuum hoses. I have checked with many transmission shops and even the local Jaguar dealerships, and no one wants to take it on to do the initial diagnosis. My question is: can anyone refer me to a shop in the Toronto area? I am fairly competent with vehicles (not a mechanic) but I don't have the energy anymore at my age to undertake this task?